The PAS-3X has a flat spot near the center of the bass and treble knob's rotation. If you turn both the bass and treble knobs slowly all the way from one end to the other, you can usually feel that "null" position. If the bass and treble knobs have the same feel all the way through their rotation then you have a PAS-3.

Bob Latino wrote:The PAS-3X has a flat spot near the center of the bass and treble knob's rotation. If you turn both the bass and treble knobs slowly all the way from one end to the other, you can usually feel that "null" position. If the bass and treble knobs have the same feel all the way through their rotation then you have a PAS-3.

Bob

Another way to tell: The PAS-3's tone control knobs will rotate through the same size arc as the balance control.

The PAS 3X tone controls do NOT have a mechanical detent at center. There are a few external clues, however, along with obvious internal differences. Here's an article that describes how to tell if it's a PAS 3 or 3X:

http://audioregenesis.com/documents/Dynaco%20PAS%203%20or%203X.pdf

As far as "originally" being a PAS 2 or PAS 3/3X - The PAS 2 is usually typified by the brass faceplate, however Dynaco did supply upgrades kits for both the faceplate, and later, 3X tone controls, so any particular PAS, of unknown background, may have started life as a PAS 2, or 3, and been upgraded at some point.

audioregenesis wrote:The PAS 3X tone controls do NOT have a mechanical detent at center. There are a few external clues, however, along with obvious internal differences. Here's an article that describes how to tell if it's a PAS 3 or 3X:

http://audioregenesis.com/documents/Dynaco%20PAS%203%20or%203X.pdf

As far as "originally" being a PAS 2 or PAS 3/3X - The PAS 2 is usually typified by the brass faceplate, however Dynaco did supply upgrades kits for both the faceplate, and later, 3X tone controls, so any particular PAS, of unknown background, may have started life as a PAS 2, or 3, and been upgraded at some point.